1. Field of the Invention:
This invention relates to variable magnification finders and, more particularly, to finders for lens shutter type cameras, video cameras, or the like in which the magnification of the field of view of the finder is varied over an extended range at high values of magnification, while still maintaining good optical performance throughout the extended range.
2. Description of the Related Art:
In the past, as the finder of which the magnification of the field of view is made variable to produce a variable magnification finder, variable magnification finders in which the variation of the magnification is performed by making such part of the objective lens, or a lens unit, movable in relation to a variation of the magnification of the photographic system have been proposed in, for example, Japanese Laid-Open Patent Application No. Sho 61-160713.
Also, observation systems such as telescopes and binoculars in which part of the eyepiece lens, or a lens unit, is made movable have been proposed in, for example, Japanese Patent Publication No. Sho 36-2723.
In the past, in the camera whose photographic system and finder system are separately constructed, when the photographic system is a variable magnification system, the use of the variable magnification finder is arranged so that the magnification of the field of view of the finder varies with a variation of the image magnification has been desired for shooting.
In this case, because of incorporation into the camera, what is desired is small size and, moreover of such a form as to easily obtain a predetermined ratio of magnification variation.
In recent years, in the field of art of compact cameras, such powerful zoom lenses which exceed 3.times.in the magnification variation ratio are anticipated. Also, various proposals for cameras having a capability for recording trimming information on film have been made. In accompaniment with this, the demand for a variable magnification finder having a high magnification variation ratio is much greater.
However, the conventional variable magnification finder in which the magnification is varied by the objective lens has a relatively small magnification variation ratio. To realize such a high magnification variation ratio as to exceed, for example, 3x, the lens diameter and the number of lens elements rapidly increases. Thus, the finder system tends to increase in bulk and size. Also, the lens structure tends to become complicated. Moreover, it has been very difficult to stabilize the variation in the aberrations with the variation of the magnification.
Also, in a camera having the capability of recording the trimming information on the film, the prior art shows that although the trimming information is provided by moving the objective lens to vary the finder magnification in response to a variation of the image magnification of the photographic lens, the field of view of the finder does not vary. This constituted another drawback that the effect of the trimming function is not communicated to the observer.